The Epidemiology of Dementia project brings the strengths of the Framingham Study to the study of the incidence, precursors and manifestations of Alzheimer's Disease (AD) and other types of dementia. The investigators propose to extend the present study to the children (and their spouses) of the original Framingham cohort who are members of the Framingham Offspring cohort. The investigation of AD and dementia in the offspring presents a unique opportunity to examine and follow longitudinally a cohort whose parents were systematically evaluated neurologically and whose dementia status was established. The availability of DNA samples for both the parents and offspring cohorts and knowledge of the family relationships will facilitate genetic studies of AD and dementia. In addition, during the past 40 years in the cohort, and 20 years in the offspring, risk factor data pertinent to the study of AD and dementia have been collected systematically and routinely on all subjects. These include: personal habits, medical and family history, cardiovascular risk factors and documented cardiovascular events, and stroke events which have been collected in considerable detail in a comprehensive stroke study.Many blood chemistry determinations have been made including TSH, apolipoproteins including the apo E isoforms, homocyst(e)ine, folate and vitamin B12. The study of cognitive decline in the Framingham Study which began on Exams in 1976, has determined the prevalence and incidence of AD and dementia. Subjects have been evaluated at home, in nursing homes and chronic hospitals as well as in the Framingham Study clinic. With advancing age, particularly in the presence of stroke or dementia, increasing numbers of study subjects will need to be seen at their residence. MRI scans will be performed on cases and controls to identify ischemic changes The number, site, size and location of the ischemic changes will be related to dementia and to specific patterns of neurologic and neuro- psychological performance using a standard MRI reading protocol developed by the Cardiovascular Health Study of the NHLBI.